In recent years, the number of car accidents has been decreasing. However, the number of accidents caused by health condition has been increasing. Here, the accidents caused by health condition refer to “accidents where due to drivers' diseases, the drivers were unable to continue driving their cars” (car accident reporting rules, Article 2, Item 9). The drivers' diseases in the accidents caused by health condition mainly include a myocardial infarction, a subarachnoid hemorrhage, a cerebral hemorrhage, a stroke, a heart failure, etc., and only brain and heart diseases form a majority. When drivers suffer from such diseases during driving, it inevitably leads to serious accidents and thus complete health care is strongly demanded.
In addition, about 15% of the accidents caused by health condition are accidents caused by dozing at the wheel. As with the case in which drivers suffer from a brain disease or a heart disease during driving, dozing at the wheel is highly likely to lead to serious accidents. Thus, various methods for preventing dozing at the wheel are studied. Specifically, there are, for example, a method in which driver's physical information such as a heartbeat and respiration is detected by a sensor mounted in a car and the physical information is analyzed to detect driver's drowsiness, and a method in which a driver's face image is photographed by a camera and dozing off is detected from eyelid condition, etc. For example, a “dozing prevention warning device that senses a moment of a person going into a dozing state, from his/her brainwave frequency or heart rate and gives a warning” is disclosed in Patent Document 1 (Abstract). In addition, for example, a “driver's state estimation device that detects driver's heart beat intervals and estimates a driver's state based on whether there is a change in the beat intervals” is disclosed in Patent Document 2 (Abstract).